Certain building materials can be prepared from cementitious mixtures based on portland cement and can contain additives to enhance the properties of the materials. Fly ash is used in cementitious mixtures to provide enhanced durability and reduced permeability of the cementitious products. In addition to imparting improved performance properties, the use of fly ash is desirable because it is a recyclable product and would otherwise be a waste material. Furthermore, fly ash is less expensive than portland cement. Thus, there is a desire to provide high strength building products that are based on fly ash.